In 2012, look for the Unified Communications (UC) industry to finally evolve away from using terms like “calls” and “trunks” and replace it with the concept of a “session.” I believe this to be an important step on the road to more pervasive UC deployments, particularly mobile UC.

Why do I believe that? The first step in believing this is to understand what a session is. With voice over IP (VoIP) and UC, the industry uses terms like “calls” to discuss the features in a UC solution. However, this term is a throwback to legacy communications and is used to make new UC solutions look like an old PBX. It reminds me of when I was in college taking a software development class and the lab instructor referred to lines of codes as “job cards.” There were no cards, just lines of code. Similarly today, we aren’t making calls in an all IP world.

What happens when you pick up a VoIP phone and “dial” (another term that needs to go away), is that the system establishes a SIP session between the two end points. The session might be used to transmit voice only but could also be used for video or chat or anything else that uses SIP as its transmission protocol. The main point though is that the system uses SIP as the underlying communications protocol. SIP is a protocol that functions at the IP layer of the OSI stack—this itself is an important point. Things done at the IP layer are portable and dynamic, where as things done at layer 2 are not. IP based communications can maintain its state, layer 2 ones do not.

Consider any other IP based application—the Internet or e-mail for example. There’s no manual intervention needed when a user moves. The user picks up the device, attaches to a network and, like magic, is connected to the application. This is the big benefit of running applications at the IP layer. The state is maintained, making the connection dynamic and mobile.

Once a company rolls out a SIP based communications server, it becomes possible to bring all the inherent characteristics of IP based to the world of communications. Thinking about the vision of UC, this allows organizations to mobilize communications. I don’t mean just making it wireless, that can be done today, but making the service move between devices.

In my mind, this is the single biggest difference between making UC mobile instead of wireless. The SIP session makes it possible to deliver UC application to any device over any network–a UC utopia. Without that, we’re just making calls and haven’t really changed anything. I would look for the concept of the session and the overall importance of it to become a bigger and bigger theme in 2012 for the UC industry.

Zeus, I believe you mean to day, “SIP is a protocol that functions on top of the IP layer of the OSI stack—this itself is an important point.”

Then the comparison between IP and Ethernet addressing has to do with logical addresses that can easily change (think DHCP assigned dynamic IP address) and physical Media Access Control (MAC) addresses which are physically burned into the card and set by the manufacturer (an analogy would be the old home phone number assigned to you by the telco – not easily changed but assigned/wired to a physical port)

As you state, SIP uses a logical address (handle or SIP URI) which is mapped dynamically to the end-users IP address (via the SIP Proxy/Location Database) which itself is ultimately mapped to the end-users physical Ethernet address (via Address Resolution Protocol aka ARP).